The diffusion of mobile electronic devices such as tablet terminal devices and portable game devices leads to wide use of touch panels that detect input coordinates in the display screen. A four-wire or five-wire resistive touch panel detects input coordinates based on the electric potential of the resistance film corresponding to a pressed point on the input surface of the touch panel.
The detected input coordinates, however, have deviations from the actual coordinates of the pressed point because the equipotential lines in the resistance film are curvilinearly distorted due to the effect of the resistance values of the electrodes located in the edges of the resistance film. The deviation of the detected input coordinates can be reduced by using electrodes having a low resistance value, but an overcurrent flows through an electronic component, such as a transistor coupled to the electrode, and thus may break it. Furthermore, the use of an electronic component having a high pressure resistance is possible, but increases the cost of the touch panel device.
To address the above described problem, Japanese Patent Application Publication Nos. 2009-48277, 2005-134992, and 2007-503037 (Patent Documents 1, 2, and 3) disclose methods of correcting input coordinates on a touch panel.